Error: timed out waiting for server to start from the ollama command on Windows means the client found no server at the address it uses, launched the Ollama app to start one, and gave up after five seconds. Check two things: that something listens on 127.0.0.1:11434, and that OLLAMA_HOST is not sending your terminal somewhere else.

If $env:OLLAMA_HOST prints a value, clear it with $env:OLLAMA_HOST = $null and run the command again. If nothing listens on 11434, start Ollama from the Start menu (the llama icon appears in the notification area) or run ollama serve in a second terminal.

The error

PS> $env:OLLAMA_HOST = "127.0.0.1:11435"
PS> ollama list
time=2026-10-22T18:01:24.367+05:30 level=INFO source=app_windows.go:281 msg="starting Ollama" app=C:\...\Programs\Ollama version=0.40.6 OS=Windows/10.0.26300
time=2026-10-22T18:01:24.367+05:30 level=INFO source=eventloop.go:310 msg="existing instance found, not focusing due to startHidden"
time=2026-10-22T18:01:24.367+05:30 level=INFO source=app_windows.go:79 msg="existing instance found, exiting"
Error: timed out waiting for server to start

A log-rotation warning printed above these lines is left out, and the user folder in the path is shortened; nothing else changed.

Why it happens

Every ollama subcommand except serve is a client that sends HTTP requests to a server, by default at 127.0.0.1:11434. On Windows, a refused connection does not fail at once: the client launches ollama app.exe, the tray app that sits next to ollama.exe, then polls the server every half second for five seconds (that is waitForServer in the Ollama source). If nothing answers, you get this message. Both test commands took 5.1 seconds to fail.

The three INFO lines are the second copy of the app talking: it found the tray app already running and exited. The real server was healthy on 11434, but the client was asking 11435. The same refusal in older releases read could not connect to ollama app, is it running?; the source at tag v0.5.7 has that wording. An address that is not on your machine skips the app launch: a host name that does not resolve failed at once with no such host, an unreachable IP after 21 seconds with connectex: A connection attempt failed.

The fix

PS> $env:OLLAMA_HOST
127.0.0.1:11435
PS> $env:OLLAMA_HOST = $null
PS> Get-NetTCPConnection -LocalPort 11434 -State Listen | Select-Object LocalAddress, LocalPort, OwningProcess
LocalAddress LocalPort OwningProcess
------------ --------- -------------
127.0.0.1        11434          3220
PS> ollama list
NAME                       ID              SIZE      MODIFIED
qwen2.5:3b                 357c53fb659c    1.9 GB    50 seconds ago
llama3.1:8b                46e0c10c039e    4.9 GB    4 weeks ago

The list is shortened to two of six rows. If the variable returns in every new terminal, it is stored in your account: check [Environment]::GetEnvironmentVariable("OLLAMA_HOST","User") and remove it under "Edit environment variables for your account". The OLLAMA_HOST explainer covers what the variable does on both sides.

If Get-NetTCPConnection returns nothing for 11434, no server is running: start the app and try again. To prove that half, ollama serve was started by hand on 127.0.0.1:15436 with OLLAMA_HOST set to that address; its log said Listening on 127.0.0.1:15436 (version 0.40.6), and the same ollama list answered with an empty table instead of the timeout.

How it was reproduced

On Windows 11 with Ollama 0.40.6 running as the tray app on 127.0.0.1:11434, untouched throughout, in Windows PowerShell 5.1. Rather than stop the app, the client was pointed at 127.0.0.1:11435, where Get-NetTCPConnection showed no listener; ollama list and ollama run qwen2.5:3b both printed the error and exited with code 1. The fix was confirmed by clearing the variable, and by a hand-started server on 15436 with its own empty model folder, stopped afterwards by its process id. The case of an app that is not running at all was not exercised, because the tray app was not ours to stop.

Frequently asked

What does 'timed out waiting for server to start' mean in Ollama?
The ollama command could not connect to a server, launched the Ollama app to start one, and no server answered within five seconds. Either the app could not start its server, or the command is looking at the wrong address because OLLAMA_HOST is set.
How do I check if Ollama is running on Windows?
Look for the llama icon in the notification area, or run Get-NetTCPConnection -LocalPort 11434 -State Listen in PowerShell. With a server running, ollama --version prints the version without any warning.
Is 'could not connect to ollama app, is it running?' the same error?
Yes. Older Ollama releases printed that message when the client could not reach a server and could not start one; the source at tag v0.5.7 has it. Current releases return the timeout message instead. The checks and the fixes are the same.

More decoded errors in the Fixes category. The Linux and WSL version of this failure is could not connect to ollama server.